This invention relates to structural members adapted to be used as beams, joists, studs, posts, lintels, columns or as base and top plate members.
It is known to provide composite structural members designed to reduce the amount of solid wood fiber used and to improve the load bearing capacity of the member, as compared to solid lumber. U.S. Pat. No. 5,079,894 to Lau discloses such a structural member having a X-shaped cross section and comprising two isosceles triangle-shaped flanges bonded to opposite sides and ends of parallelogram-shaped web.
However, Lau""s use of wedge-shaped flanges and a parallelogram-shaped web limits the load bearing capacity of the member on two of its four sides as such loads are borne on the narrow longitudinal edges of the flanges and web. This in turn limits the ability to use the member in horizontal load bearing applications, or to effectively combine several such members in side by side relationship to form multi-unit composite members such as would be useful for example to produce posts or columns.
Lau also suggests that the flanges of the structural member may be produced simply by diagonally (WORD USED BY LAU) halving 2xc3x973 or 2xc3x974 lumber to produce two isosceles triangular wedges. But in fact, more than one cut would be required to do so. As a result, fabrication of the structural member is not as simple as Lau suggests, nor is it as cost effective as is the present invention in terms of manufacturing steps or the volume of solid wood fibre consumed per unit.
It is therefore an object of the present invention to provide an improved composite structural member made of wood or wood fibre products wherein economical use of solid wood fibre is made and which is relatively easy to manufacture. It is yet a further object of the invention to provide a simple method of producing a composite structural member from solid lumber having standard dimensions.
It is a further object of the invention to provide a composite structural member which has good load bearing capacity on substantially all of its sides and which is capable to being combined with other such members into a multi-unit member.
It is yet a further object of the invention to provide a useful cross sectional profile of a structural member which may selectively be made using materials other than wood or using a combination of wood and such other materials.
According to the preferred embodiment of die invention, a structural member is provided comprising a generally Z-shaped cross section. Two flange members are bonded to opposite sides and opposite ends of a diagonal web. Preferably, the flange members and the diagonal web are made of wood or wood fibre products and xe2x80x9cthe flangexe2x80x9d members are cut from standard dimensional lumber.
Each flange member has one surface which is bonded to the web and at least two additional surfaces at right angles to one another. The cross section of the web is six sided, each end of the cross section including a side which is continuous with one of the right angled sides of its associated flange member and another side which acts as a side load bearing surface for the structural member.
In another aspect of the invention, the structural member has a cross sectional profile which is defined within an imaginary rectangle, and has a diagonal web member and two flange members disposed on opposite sides of the web member. Each of the flange members has two sides which are coplanar with the sides of the imaginary rectangle and the web portion has at least four surfaces which are coplanar with the sides of the imaginary rectangle.
In another of its aspects, the invention comprises a composite assembly of such structural members secured in side by side relationship. This is particularly useful when each structural member has a cross sectional profile whose longer side has a length which is an even multiple of the length of its shorter side.
According to a method of making the structural member according to the invention, a piece of solid lumber having a rectangular cross-section is sectioned so as to produce at least two equal segments. Each has interior angles consisting of two right angles, one acute angle and one obtuse angle. An elongated web having a generally rectangular cross section and two opposed planar surfaces is provided. Two longitudinal cuts are made obliquely across the planar surfaces of the web substantially at one edge of the web. The two cuts are at a right angle to one another. Two additional longitudinal cuts are made obliquely across said planar surfaces substantially at the other edge of the web. They too are at a right angle from one another. The at least two equal segments are then bonded to opposite sides and opposite ends of said web.
The sectioning step described above may in fact produce only two equal segments by performing a single longitudinal oblique cut through the central longitudinal axis of the lumber. Four or more equal segments may also be obtained depending on the width of the lumber and the desired dimensions of the resulting structural member. In the case of four equal segments, the sectioning step of the method comprises the steps of:
longitudinally sectioning said piece of lumber into two equal pieces each having a rectangular cross section;
longitudinally sectioning each of said two equal pieces with an oblique cut so as to produce four of said equal segments.
The present invention minimizes the use of solid wood, presents good side load and end load bearing capacity, allows composite structural members to be produced and provides the advantage of ease of manufacture with a minimum number of cuts.
In another of its aspects, the invention comprises an elongated, integrally formed structural member having cross section comprising a diagonal web portion having major opposed planar surfaces, and two edge portions extending along opposite lateral edges of said web member, characterized in that each of said edge portions comprises two parallel and spaced surfaces extending in a same direction from said web portion, and a third surface extending perpendicularly to said two parallel between the ends of said two parallel surfaces. The web portion includes at least two surfaces which are parallel to said third surfaces.
Other aspects of the invention will be appreciated by reference to the description of the preferred embodiments which follows and to the claims.